Hierarchical modulation for unicast streams

ABSTRACT

Hierarchical modulation is performed by an access node in a communication network, by identifying, by the access node, a plurality of user devices in the communication network for hierarchical modulation reception, and sending, via a transceiver in the access node, control information to each of the identified user devices, the control information comprising an identification of a shared radio resource for use by two of the identified user devices in support of hierarchical modulation reception.

CROSS-REFERENCE TO RELATED APPLICATION

The present application also claims priority to U.S. Provisional PatentApplication No. 61/905,784, filed on Nov. 18, 2013, and entitled“Hierarchical Modulation for Unicast Traffic,” the disclosure of whichis herein incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of Invention

This invention relates to telecommunications and more particularly tohierarchical modulation for unicast traffic.

2. Description of Related Art

Hierarchical modulation, also called layered modulation, is a signalprocessing technique for multiplexing and modulating multiple datastreams into one single symbol stream. The idea is that one stream(i.e., the base-layer, also called the High Priority stream, HP) ismodulated with a robust modulation technique and one or more otherstreams (i.e., enhancement-layers, also called Low Priority streams, LP)are synchronously superimposed on the base layer with a less robustmodulation. When hierarchical modulation signals are transmitted, userdevices with good reception and with hierarchical modulation enabledreceivers can demodulate the base and enhancement layers, while userdevices with poor reception or conventional receivers can demodulateonly the base layer (the HP stream). Hierarchical modulation has beenused in, among other things, video broadcasting such as digital videobroadcasting-terrestrial (DVB-T), digital video broadcasting-handheld(DVB-H), and MediaFLO by Qualcomm Incorporated, the implementation ofwhich are readily apparent to one of ordinary skill in the art.

FIG. 1 illustrates a conventional video broadcasting hierarchicalmodulation system 100. Broadcasting refers to the transmission of amessage to all receivers (e.g., every device on the network)simultaneously. Here, the base layer is associated with a video baselayer that is needed for all receivers (e.g., user equipment UE₁ 120 andUE₂ 130, although any number of UEs may be implemented), which is sentfrom a base station 110 with high robustness to guarantee properdecoding by all receivers even with poor channel quality. Enhancedlayers, which only contribute to the quality of the received video, aresent with less robust techniques. Hence, receiving devices with goodchannel conditions, e.g., UE₁, can receive the full video signal, whilethose devices with poor channel conditions at the edge of a cell, e.g.,UE₂, will only manage to get the base layer. A UE may also be referredto as a user device herein.

FIG. 2A illustrates a constellation diagram of a basic implementation ofhierarchical modulation. Here, the base layer is viewed as quadraturephase shift keying (QPSK also referred to as quadrature amplitudemodulation QAM4) (shown left) with two bits per symbol data carryingcapacity, while the enhanced layer is provided by the additional twobits per symbol data carrying capacity (4 bits per symbol total) ofquadrature amplitude modulation QAM16 (shown right with base layer bitsand enhanced layer bits separated by the “|” character for clarity).Receiving the base layer requires only determining which quadrant thesymbol resides in, and can be performed by demodulating the receivedsignal as if it were transmitted as QPSK. Receiving the enhanced layerrequires demodulating the received signal as QAM16 to determine theposition within the quadrant to resolve the additional two bits of datacarrying capacity.

FIG. 2B shows an example of hierarchical modulation in which the baselayer and enhanced layer are mapped into QAM64, which logically appearsto be a QAM16 (represented by the 16 square constellation points in eachquadrant) constellation with 4 bits per symbol data carrying capacity ontop of a QPSK (represented by the gray circles) constellation with 2bits per symbol data carrying capacity realized by a single transmissionof a QAM64 constellation with 6 bits per symbol data carrying capacity.In this case, to receive the enhanced layer it is necessary to receivethe signal as QAM64, but to receive the base layer it is only necessaryto receive the signal as QPSK. One skilled in the art would understandthat different variants, such as receiving the base layer as QAM 16 andthe enhanced layer as the remaining 2 bits per symbol carrying capacityof a QAM64 constellation, are possible.

While traditional hierarchical modulation has been used in broadcasting,it has not been used in non-broadcasting communications system such as,but not limited to unicast transmission. Unicast transmission refers tothe sending of messages to a single network destination. It would behelpful to find a way to use hierarchical modulation in a non-broadcastcommunications system to better utilize bandwidth capacity.

SUMMARY OF THE INVENTION

According to an aspect, a method is provided in which hierarchicalmodulation is performed by an access node in a communication network, byidentifying, by the access node, a plurality of user devices in thecommunication network for hierarchical modulation reception, andsending, via a transceiver in the access node, control information toeach of the identified user devices, the control information comprisingan identification of a shared radio resource for use by two of theidentified user devices in support of hierarchical modulation reception.

In another aspect, a method is provided for hierarchical modulationreception by a user equipment within a communications network, whichincludes receiving, via a transceiver in the user equipment, controlinformation from an access node indicating an assigned layer ofhierarchical modulation designated for the user equipment, receiving,via the transceiver in the user equipment, a hierarchical modulatedtransmission from the access node, and utilizing only the assigned layerof the received hierarchical modulated transmission.

In another aspect, a method is provided for hierarchical modulation oftwo data streams transmitted from a user device in a communicationnetwork, which includes sending, via a transceiver in the user device, arequest for uplink bandwidth to an access node in the communicationnetwork, receiving, via the transceiver, an uplink bandwidth allocationprovided in a downlink channel from the access node, multiplexing, atthe user device, a base layer data stream and an enhanced layer datastream into a single multiplexed data stream, and transmitting, via thetransceiver, the single multiplexed data stream to the access node inthe uplink bandwidth allocation.

According to another aspect, a method is provided for receiving, at anaccess node in a communication network, a single multiplexedhierarchical modulation data stream transmitted from a user device,which includes receiving, via a transceiver in the access node, arequest for uplink bandwidth from the user device, sending, via atransceiver, an uplink bandwidth allocation in a downlink channel to theuser device, receiving the single multiplexed hierarchical modulationdata stream from the user device in the uplink bandwidth allocation,wherein the single multiplexed hierarchical modulation data streamcomprises a base layer data stream and an enhanced layer data stream,and extracting the base layer data stream and the enhanced layer datastream from the multiplexed hierarchical modulation data stream.

The foregoing, and other features and advantages of the invention, willbe apparent from the following, more particular description of thepreferred embodiments of the invention, the accompanying drawings, andthe claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, the objectsand advantages thereof, reference is now made to the ensuingdescriptions taken in connection with the accompanying drawings brieflydescribed as follows.

FIG. 1 illustrates hierarchical modulation in a conventional videobroadcasting system;

FIG. 2A illustrates a constellation diagram of an implementation ofhierarchical modulation using QAM4 and QAM16;

FIG. 2B illustrates a constellation diagram of an implementation ofhierarchical modulation using QAM4 and QAM64;

FIG. 3 illustrates a unicast downlink hierarchical modulation processaccording to an embodiment of the invention;

FIG. 4 illustrates a process for selecting UE candidates for receptionof both the basic and enhanced layer according to an embodiment of theinvention;

FIG. 5 illustrates an orthogonal frequency-division multiplexing (OFDM)transmitter according to an embodiment of the invention;

FIG. 6 illustrates an OFDM receiver according to an embodiment of theinvention;

FIG. 7 illustrates a hierarchical modulation enabled multiple inputmultiple output (MIMO) OFDM transmitter according to an embodiment ofthe invention;

FIG. 8 illustrates a hierarchical modulation enabled MIMO single carrierfrequency division multiple access (SC-FDMA) transmitter according to anembodiment of the invention;

FIG. 9 illustrates a hierarchical modulation enabled MIMO OFDM receiveraccording to an embodiment of the invention;

FIG. 10 illustrates a hierarchical modulation enabled MIMO SC-FDMAreceiver according to an embodiment of the invention;

FIG. 11 illustrates a hierarchical modulation enabled SC-FDMAtransmitter, such as might be used in a UE, according to an embodimentof the invention;

FIG. 12 illustrates a hierarchical modulation enabled SC-FDMA receiver,such as might be used in a base station, according to an embodiment ofthe invention;

FIG. 13 illustrates a process of uplink hierarchical modulation for twodata streams from the same UE according to an embodiment of theinvention;

FIG. 14 illustrates a UE initiated process for hierarchical modulationin an uplink for two data streams from the same UE according to anembodiment of the invention;

FIG. 15 illustrates a base station initiated process for hierarchicalmodulation in an uplink for two data streams transmitted from the sameUE to the base station according to an embodiment of the invention;

FIG. 16 illustrates a constellation diagram of an implementation ofhierarchical modulation according to an embodiment of the invention;

FIG. 17 illustrates rotated hierarchical modulation according to anembodiment of the invention;

FIG. 18 illustrates rotated hierarchical modulation according to anotherembodiment of the invention;

FIG. 19 illustrates a constellation diagram of hierarchical modulationmuting 32 constellation points according to an embodiment of theinvention;

FIG. 20 illustrates network system in which with aspects of theinvention may be implemented;

FIG. 21 illustrates an access node in accordance with aspects of theinvention; and

FIG. 22 illustrates a terminal node in accordance with aspects of theinvention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Aspects of the present invention and their advantages may be understoodby referring to FIGS. 3-22, wherein like reference numerals refer tolike elements. The descriptions and features disclosed herein can beapplied to various communication systems, including wireline andwireless networks. For example, the embodiments disclosed herein can beused with cellular 2G, 3G, 4G (including Long Term Evolution (LTE), LTEAdvanced, and IEEE 802.16 wireless-network standards referred to as“WiMAX”), cellular backhaul, IEEE 802.11 wireless local access networkstandards (“Wi-Fi”), Ultra Mobile Broadband (UMB), cable modem, andother point-to-point or point-to-multipoint wireline or wirelesstechnologies. For concise exposition, various aspects are describedusing terminology and organization of particular technologies andstandards. However, the features described herein are broadly applicableto other technologies and standards.

The following convention is oriented towards a reception scheme in amobile device, i.e., a user equipment (UE), for describing multiplexedstreams in hierarchical modulation. As used herein, the term “UE” mayalso refer to a terminal node, a mobile device, a subscriber station, amobile phone, a cellular phone, or other user operated communicationdevice. As an example, in a hierarchical modulation system utilizingQPSK modulation on the base layer and a higher order modulation toenable the enhanced layer, one of the UEs will aim to receive only thebase layer using QPSK reception. Another UE will aim to receive the fullsignal using higher order modulation (e.g. QAM64 to give an additional 4bits per symbol data carrying capacity) reception. That is, the 2 bitsper symbol base layer and the 4 bits per symbol enhanced layer aremapped into a QAM64 modulated, over the air signal (transmitted andreceived) as illustrated in FIG. 2B.

The use of link adaptation in the downlink for unicast traffic causes abase station (e.g., evolved NodeB or eNB in case of LTE) to adjust themodulation/coding in the transmission based on the channel quality forthe UE. As used herein, the term “base station” may also refer to anaccess node, an evolved NodeB or eNB in case of LTE, or othertransmitting network node. A UE with poor channel quality is assignedQPSK modulation in the radio resources that are allocated to it.Additional bits are “piggy backed” on these radio resources to other UEswith better channel quality using hierarchical modulation. This means,for the radio resources carrying unicast traffic via more robustmodulation schemes in the downlink, another stream can be superimposedtargeting another UE. This leads to enhanced overall throughput of thecommunications system. The improvement in the throughput may come at theexpense of reduced signal to noise ratio (SNR) for the base layer.However, to make the aggregate effect more favorable, the presentinvention can be applied on UEs that have been determined to be able tocurrently tolerate such reduction in the SNR or can tolerate furtherincrease in the bit error rate (BER). The structure of the controlchannel information (e.g., downlink control information or DCIs in caseof LTE) describing the downlink allocation to UEs is changed to allowmultiple allocations of the same radio resource to multiple UEs. Thistechnique improves utilization of radio resources, which will lead toimprovement in system throughput. Moreover, UEs can share a radioresource to receive short messages not requiring full utilization of thesmallest allowable radio resource (e.g., a single LTE resource block).For example, one UE that does not need the entire radio resource, say atQAM16, receives messages at the equivalent of QAM4 (by processing only 2of the 4 bits per symbol), while another UE receives messages at QAM16(by processing all 4 bits per symbol). This can be used in, for example,machine to machine (M2M) technologies such as, but not limited to,short, messages sent to a machine requesting a change in behavior orsending acknowledgment (ACK) messages to information previously sent bythe machine on the uplink.

FIG. 3 illustrates a unicast downlink hierarchical modulation process300 according to an embodiment of the invention. Process 300 begins bythe base station receiving (step 310) the capabilities of the UEs.Capabilities include, but are not limited to whether hierarchicalmodulation and/or detailed measurement reports are supported by therespective UE. As part of those capabilities, the base station may alsoidentify levels of features related to hierarchical modulation supportedby the respective UE. The base station uses this information inidentifying a UE as a candidate for shared allocation using hierarchicalmodulation. This step is optional in a system that requires all UEs tosupport a hierarchical modulation scheme.

The UEs are then configured (step 320) for measurement collection. Here,the UEs are configured to provide the base station with a detailedmeasurement report, which may include measurements of different downlinksignal properties (“signal measurements”) and one or more recommendedmodulation schemes. This step is optional in a system in which all UEsprovide a standard report that includes sufficient information tosupport the hierarchical modulation scheme. For communication systems inwhich the UEs report the downlink channel quality in terms of rawinformation such as, for example, SINR (i.e., the power of a certainsignal of interest divided by the sum of the interference power and thepower of some background noise) or received signal strength indication(RSSI), no change may be needed to the reporting format. However, somechanges may be applied to precision, thresholds, or periodicity ofreporting. For a communication systems (such as LTE) in which the UEprocesses this raw information to determine a recommendedmodulation/coding scheme, a detailed measurement report may be utilized.In the latter case, the recommended modulation scheme is determined byanalyzing the reception margin above a predetermined minimum necessarysignal quality needed to support the recommended modulation. Forinstance, if an SNR of N is necessary to receive the recommendedmodulation and the UE has an SNR of N+Y, then Y is the reception margin.Such information indicates whether the receiver is able to tolerate somedegradation of SINR while maintaining the recommended modulation.

In an embodiment of the invention, the base station identifies the UEsthat support detailed measurement reports for hierarchical modulation,and sends a configuration message to those UEs (or a subset of them) tosend such detailed measurement reports. On the UE side, upon receiving aconfiguration message, the UE will set its configuration to senddetailed measurement reports to the base station. In an embodiment ofthe invention, the configuration message includes raw or more preciseSINR and/or RSSI, reception margin above the recommended modulation, orlist of tolerable hierarchical modulation combinations. Alternatively,the UE has already informed the base station whether or not it supportshierarchical modulation or detailed measurement reports.

The signal measurements and reports from the UEs are then collected(step 330) by the base station. Some of these reports may be thestandard report while others may be detailed measurement reports. For aUE that supports hierarchical modulation and is configured to send adetailed measurement report, the UE prepares and sends a measurementreporting message with the UE's recommendation for the selectedmodulation in a periodic or aperiodic/event driven fashion. The detailedmeasurement report may include further information to give more detailedprecision about the recommended modulation/coding. For example, adetailed measurement report may include an information element inaddition to the recommended modulation/coding to specify the UEtolerance to a further degradation in the SINR due to superimposing ofanother layer via hierarchical modulation (HM). This measure oftolerance can be stated via a simple flag (allow, disallow), via aquantitative value such as a value of 1 to 4, or via specifying whatmodulation scheme the UE will allow to be superimposed on its signal,such as a UE that is recommending a QPSK modulation for reception of itsdata and a QAM16 modulation to be further superimposed on its signal.The UE may specify the options (does not allow HM, allow QAM16 only,allow QAM64) using one or more bit fields in a message. In anotherembodiment of the invention, the detailed measurement report includes adefinition of a modulation/coding encoding to communicate the same typeof information. This means the message format may remain the same, butthe modulation/coding schemes may be extended to support the moreprecise reporting. In another embodiment of the invention, the detailedmeasurement report provides the raw data (SINR, . . . ) in addition toor instead of the recommendation.

In the next step, the base station identifies (step 340) candidate UEsfor application of hierarchical modulation. FIG. 4 illustrates a process400 for selecting UE candidates for reception of the basic layer and/orenhanced layer according to an embodiment of the invention. In theprocess 400, each UE candidate is a UE that has data pending at the basestation for transmission to the UE. UEs are excluded (step 401) andconsidered as non-candidates whose service level agreements (SLAs) orquality of service (QoS) profiles do not allow participating inhierarchical modulation. Note that this will mean that QoS and/orservice level agreement (SLA) may have some indicators for whether ornot hierarchical modulation is acceptable for this UE or bearer, i.e.,set of network parameters. Such indicators may be optional in systems inwhich all UEs are considered to be candidates for hierarchicalmodulation regardless of QoS or SLA. The remaining UE candidates arethen distributed (step 402) based on the UEs' selected modulationschemes as follows.

A communications system implements a finite set of modulation techniquesamong its nodes. For example, QPSK, QAM16, and QAM64 may be implemented.Within this example set of modulation techniques, QPSK is considered themost robust technique and QAM64 is considered the least robusttechnique. No matter what types of modulation techniques are employed asa set within a communications system, one modulation can be consideredthe most robust and another one the least robust within the set. Amodulation scheme is more robust if it can tolerate more noise,interference, etc. and still be received as compared to anothermodulation scheme.

For UEs operating at the most robust modulation scheme, e.g., QPSK, themeasurement report for each UE is checked (step 410) to see ifhierarchical modulation is currently allowed given the signal qualityreported. The measurement report indicates, or may be used to determine,that the UE has reception margin, i.e., the UE can tolerate some signaldegradation due to adding an enhanced layer. In other words, the UE isphysically capable of receiving a signal comprised of both the base andenhanced layers and demodulating the base layer (e.g., quadrant) in thepresence of signal quality degradation caused by the enhanced layer. Ifa particular UE's reported signal quality does not allow hierarchicalmodulation, the UE is excluded (step 411) as a candidate. If thereported signal quality allows hierarchical modulation, the UE isidentified (step 412) as a candidate for the base layer.

UEs with the least robust modulation scheme, e.g., QAM64, may beconsidered as candidates for the enhanced layer. Within this group, eachUE is checked (step 403) to see if the respective UE is capable ofsupporting hierarchical modulation, i.e., whether the UE is capable ofdemultiplexing the data represented by the enhanced layer from thecombined bitstream representing the base and enhanced layers. If aparticular UE is not capable of supporting hierarchical modulation, theUE is excluded (step 404) as a candidate. If the UE supportshierarchical modulation, the UE is identified (step 405) as a candidatefor the enhanced layer. In another embodiment of the invention, two UEsboth using the least robust (highest order) modulation could be pairedwith one downgraded to a lower modulation if the data situation madesense, e.g., insufficient data to fully utilize the resources at thehigher modulation.

All other UEs (i.e., those UEs running with other modulation schemes notconsidered to be most or least robust, e.g., QAM16) are considered ascandidates for both the base and enhanced layers. Within this respectivegroup, each UE is checked (step 406) to see if the respective UE iscapable of supporting hierarchical modulation. If a particular UE is notcapable of supporting hierarchical modulation, the UE is identified as acandidate for the base layer and follows step 410. If the UE is capableof supporting hierarchical modulation, the respective measurement reportis checked (step 407) to see if hierarchical modulation is allowed bythe current signal quality. If a particular UE's reported signal qualitydoes not allow hierarchical modulation with the UE receiving the baselayer degraded by an enhanced layer, the UE is identified (step 409) asa candidate for the enhanced layer. If the reported signal qualityallows hierarchical modulation with the UE receiving the base layer, theUE is identified (step 408) as a candidate for both the base layer andenhanced layer. Accordingly, such UEs may be added to both lists ofcandidates—base layer and enhanced layer. After the classificationprocess is complete, the candidate UEs of both layers may be organized(step 413) based on the selected modulation scheme.

The following table shows an exemplary communications system with ten(10) UEs, which are labeled as UE_1 to UE_10. The table shows somerelevant features of each UE, including their selected modulation,whether their capabilities support hierarchical modulation, whethertheir QoS or SLA supports hierarchical modulation, and whether they haveheadroom margin in their measurement report. This example assumes thatthe communication system supports only QPSK, QAM16, and the QAM64modulation schemes. For other systems using other modulation schemes,the table can be modified accordingly.

Capabilities QoS/SLA HM UE ID Support HM? Support HM? ModulationHeadroom? UE_1 Yes Yes QPSK Yes UE_2 Yes Yes QPSK No UE_3 No Yes QAM64Yes UE_4 Yes Yes QAM16 Yes UE_5 Yes No QPSK Yes UE_6 No No QAM64 No UE_7No Yes QAM16 Yes UE_8 Yes Yes QAM16 No UE_9 Yes Yes QAM64 Yes UE_10 NoYes QAM16 Yes

The following table shows the outcome of the candidate selectionprocedure for the exemplary communications system shown above. Here, UE1is a candidate for the receiving base layer via QPSK modulation. UE_4,UE_7, and UE_10 are candidates for receiving the base layer via QAM16modulation. UE_4 and UE_8 are candidates for receiving the enhancedlayer via QAM16 modulation. UE_9 is a candidate for receiving theenhance layer via QAM64 modulation. UE_4 is the only UE capable ofreceiving both the base layer and the enhanced layer. Other UEs in theabove table are not candidates for hierarchical modulation for variousreasons, such as not being able to support hierarchical modulation,being associated with a QoS/SLA that does not support hierarchicalmodulation, or not having headroom to support hierarchical modulation.For example, UE_2 is not a candidate for hierarchical modulation becauseit does not have sufficient headroom, UE_3 is not a candidate forhierarchical modulation because it does not have the capabilities tosupport hierarchical modulation, UE_5 is not a candidate forhierarchical modulation because it is associated with a QoS/SLA thatdoes not support hierarchical modulation, and UE_6 is not a candidatefor hierarchical modulation because none of its attributes(capabilities, QoS/SLA, headroom) support hierarchical modulation.

Candidates for Base Layer Candidates for Enhanced layer QPSK QAM16 QAM16QAM64 UE_1 UE_4, UE_7, UE_4, UE_8 UE_9 UE_10

Returning to process 300, once the candidate UEs are identified, thebase station then pairs (step 350) UE candidates together. In this step,the base station determines which UE candidates to pair together on thesame radio resource, which UE of the pair will be using the base layer,and which UE of the pair will be using the enhanced layer. Themodulation structure for each radio resource is also determined by thebase station for both layers. The selection of pairs can be as simple asanalyzing the lists of candidates for both the base layer and enhancedlayer and matching one from each group to share a radio resource. Forexample, a pair selection process may include the steps of: listing UEsin both base and enhanced layer in incrementing order of modulation;selecting the UE at the top of the base layer list to pair with the UEat the top of the enhanced layer list; removing both selected UEs fromboth lists (note that a selected UE may be in both lists, and should beremoved from both); and continuing this process until one of the listsis empty (or until other conditions are met, such as the case in whichthere are no remaining UE candidates in the lists that have datapending, etc.). Note that in other embodiments of the invention, one orboth UEs may be maintained in their respective lists until certainconditions are met, such as no more data pending for the UE. Applyingthis simple approach, the following is a valid selection of three UEpairs for hierarchical modulation from the outcome of the candidateselection procedure noted above. UE_1 is paired with UE_4. UE_7 ispaired with UE_8. UE_10 is paired with UE_9.

One of ordinary skill in the art recognizes that in communicationssystems utilizing multiple enhanced layers, UEs are grouped together innot pairs, but in groups in which the number of UE participants in agroup equals the number of total layers, i.e., one base layer plus thenumber of multiple enhanced layers. For instance, the 6 bits per symboldata carrying capacity of a signal modulated at QAM64 would allow a baselayer received at QPSK using 2 bits per symbol data carrying capacity, afirst enhanced layer received at QAM16 using an additional 2 bits persymbol data carrying capacity, and a second enhanced layer received atQAM64 using the remaining 2 bits per symbol data carrying capacity.

The UE selection process may be optimized based on one or moreadditional considerations. For example, the modulation level may bemaximized for the enhanced layer for as many pairs as possible.Selection of candidates to form pairs can be prioritized based on usecriteria, which may include selecting UEs in the base layer that havemore tolerance to some degradation in SINR without significant rise inBER (such as select them in a decreasing order of headroom). For UEs inenhanced layer groups, UEs are selected that have a small amount ofpending data to be delivered (whether all pending data or for a specificbearer, such as short messages to M2M devices) or optionally matched tothe available capacity of assigned radio resources. UEs may also beselected with a high demand for low latency on their transmitted data,and for which their delay budget is about to be exceeded such as lowdelay VoIP streams as determined by the UE's QoS parameters. UEs can beselected for the base layer that are running transport/application datastreams with high BER tolerance (application aware headroom adjustment),such as UDP versus TCP. UEs can be selected to achieve scheduleralgorithm criteria such as fairness or meeting guaranteed bit rate (GBR)values. Otherwise, UEs that are candidates for the base layer and havemore tolerance to signal quality degradation may be matched with UEsrunning the least robust modulation schemes, while UEs having lesstolerance to signal quality degradation may be matched with UEsoperating at more robust modulation schemes. For example, if a UE isusing QPSK with high tolerance to degradation of SINR, it can be matchedwith another UE using QAM64, while another UE using QPSK, but havingless tolerance to degradation of SINR can be matched with a UE usingQAM16.

In an embodiment of the invention, system congestion level may impactthe percentage of UEs that are matched in a hierarchical modulationscheme. System congestion can be measured based on the instantaneousamount of data pending in the queues to be transmitted in the downlink,or it can be based on some historical measurements of data pending inqueues, or it can be based on any other metric of the capacity of thebase station to meet the committed throughput to its UEs.

In another embodiment of the invention, a cost function is utilized thatis built to combine the effect of the above-mentioned criteria, or asubset of them. This cost function can be a weighted sum of the factors,with the weights reflecting the importance of each factor and itssignificance in the selection of pairs.

Upon pairing, UE control information is then prepared (step 360) fortransmission to the paired UEs via radio resource allocation messages.The role of the control information is to describe the UE allocations.Multiple UEs will be allocated the same radio resource, and thereforesome changes may be required to the format of the associated controlinformation. In an embodiment of the invention, the allocation messageintroduces new information elements, such as elements indicating thathierarchical modulation is used for certain resources and which UE is toreceive the base layer or the enhanced layer, to accommodate multipleUEs for the same radio resource. In an alternative embodiment of theinvention, multiple information elements are used for the same radioresource, one for each UE involved in the allocation of this radioresource.

Use of hierarchical modulation may result in growth of the size of theallocation messages in the control information, and this growth can bemitigated by applying hierarchical modulation on the control informationitself. UEs that can operate using an enhanced layer may receive theirresource assignment on an enhanced layer, and UEs that operate onlyusing a base layer may receive their resource assignment on a baselayer. In an aspect of the invention, an auto detection mechanism isemployed so that each UE gets its allocation without being informed inadvance of the assigned modulation for its allocation description. Forexample, each UE may try to decode the control information using thelast recommended hierarchical modulation scheme, and more robustmodulations. In an alternate aspect, the first part of the controlinformation is coded in the most robust modulation scheme, withouthierarchical modulation, so that all UEs are able to detect it. Thefirst part of the control information may describe how to find the restof the control information that contains the allocation information,wherein the rest of the control information may be transmitted usinghierarchical modulation.

The control information is then sent (step 370) from the base station tothe UEs in the downlink. Some communication systems use scrambling aspart of the transmit path, and use the UE identity as part of theutilized scrambling seed. The use of hierarchical modulation has animpact on this scheme because now the radio resource is targeted atmultiple UEs. This will require the base layer and the enhanced layer tobe combined after the scrambling module, for instance via thehierarchical modulation aware multiplexer 530 in FIG. 5, so that eachstream will be scrambled with its destined UE identity.

FIG. 5 illustrates a transmitter 500, such as might be used in a basestation, according to an embodiment of the invention. Here, thetransmitter 500 comprises an orthogonal frequency-division multiplexing(OFDM) transmit-pipeline, such as may be used in the downlink for LTE(as an example of a communications standard), on which hierarchicalmodulation can be applied. The transmitter 500 comprises encoders 510Aand 510B, scramblers 520A and 520B, a hierarchical modulation awaremultiplexer 530, a modulation mapper 540, a resource mapper 550, and aninverse fast Fourier transform algorithm (IFFT) 560. In an embodiment ofthe invention, scramblers 520A and 520B use the identity of a recipientUE as part of the scrambling seed, which is required in some standardssuch as LTE. Encoder 510A and scrambler 520A operate on the base layerstream A. Encoder 520B and scrambler 520B operate on the enhanced layerstream B. Since the base layer and enhanced layer(s) are destined todifferent UEs, the combining of the base and enhanced layer streams isperformed after the scrambling in the transmit pipeline. Scrambling andencoding may be optional. The reception path in the UE will need toimplement the reverse of the encoding and scrambling techniquesimplemented in the transmit path in the base station.

In an example (e.g., FIG. 2B), the hierarchical modulation awaremultiplexer 530 multiplexes a 2 bits per symbol base layer (e.g., to bereceived as QPSK) stream A and 4 bits per symbol enhanced layer streamB, which are then modulated into a 6 bits per symbol QAM64 constellationby modulation mapper 540. One of ordinary skill in the art wouldunderstand the multiplexing of streams of other bits per symbolcapacities into a single stream for transmission at a chosen modulation.The implementation of the modulation mapper 540 and resource mapper 550are apparent to one of ordinary skill in the art. In an aspect of theinvention, the modulation mapper 540 receives scrambled stream bits andconverts them to constellation locations, and resource mapper 550 mapsindividual QAM symbols to subcarriers.

FIG. 6 illustrates a receiver 600, such as might be used in a UE,according to an embodiment of the invention. Here, the receiver 600comprises an OFDM transmit-pipeline, such as may be used in the downlinkfor LTE (as an example of a communications standard), on whichhierarchical modulation can be applied. The hierarchical modulationenabled receiver 600 comprises a fast Fourier transform (FFT) algorithm610, a resource demapper 620, a frequency domain equalizer 630, and ademodulator 640. Implementation of the FFT algorithm 610, the resourcedemapper 620, and the frequency domain equalizer is apparent to one ofordinary skill in the art. The demodulator 640 demodulates the incomingdata stream. For example (e.g., FIG. 2B), when the hierarchicalmodulation system is utilizing a 2 bits per symbol base layer and a 4bits per symbol enhanced layer, the demodulator 640 of a UE receivingonly the base layer demodulates the signal with QPSK, receiving the 2bits per symbol base layer stream A, but the demodulator 640 of a UEreceiving the enhanced layer demodulates the signal with QAM64 andreceives all 6 bits per symbol of the both the base layer stream A andthe enhanced layer stream B.

The receiver 600 further comprises a hierarchical modulation awaredemultiplexer 650, which demultiplexes the incoming data stream intobase stream A and enhanced stream B, when receiving the enhanced layeror receiving both the base and enhanced layers. Referring back to FIG.2A, in this example, the demultiplexer 650 delineates the first two bitsof each symbol as the base layer and the last two bits of each symbol asthe enhanced layer.

Base stream A is descrambled and decoded by descrambler 660A and decoder670A, respectively. Enhanced stream B is descrambled and decoded bydescrambler 660B and decoder 670B, respectively. Descramblers 660A and660B, and decoders 670A and 670B, the implementation of all of which isapparent to one of ordinary skill in the art, may be omitted ifscrambling and coding is not utilized on the transmission side. Thecontrol information sent by the base station may be received via therespective base stream or enhanced stream, or both, that has beenallocated to the receiver 600.

Returning to process 300, the base station prepares (step 380) the datastreams for the UEs sharing the data channel. Here, the requiredmultiplexing (e.g., 2 bits per symbol on the base layer and 4 bits persymbol on the enhanced layer if following the example of FIG. 2B) isperformed on the data streams associated with the particular UEs of ahierarchical modulation pair into a single constellation in order toimplement the hierarchical modulation scheme. The multiplexed streamsare then transmitted (step 390) on the downlink channel as a higherorder modulation transmission. Each UE of the pair receives thetransmission. A UE receiving only the base layer may receive using thelower order modulation of the same bits per symbol data carryingcapacity as the base layer. A UE receiving the enhanced layer receivesusing the higher order modulation necessary to carry the base andenhanced layer and discards all layers except for its assigned layer(s).

In an embodiment of the invention, techniques such as, but not limitedto rotation of enhanced layer constellation points, which are describedbelow, may be applied to reduce the inter-layer interference inhierarchical modulation.

The inventive techniques described herein are also applicable tomultiple input/multiple output (MIMO) communications system. MIMO is theuse of multiple transmitters and receivers (multiple antennas) onwireless devices for improved performance. When two transmitters and twoor more receivers are used, two simultaneous data streams (or “layers”)can be sent, which doubles the data rate. For example, the IEEE 802.11n(Wi-Fi) wireless standard uses MIMO to increase speed to 100 Mbps andbeyond. MIMO antennas are also used in WiMAX and LTE.

Each MIMO layer can be treated as a separate instantiation ofhierarchical modulation. As such, the primary difference from anon-hierarchical modulation transmitter is the need to apply forwarderror correction (FEC) and scrambling, if any, prior to multiplexing thestreams in a hierarchical modulation aware manner in preparation formodulation. Note that with MIMO, one or more MIMO layers may havehierarchical modulation applied even if the other layer(s) are usingtraditional modulation. For each MIMO layer on which hierarchicalmodulation was applied, the receiver applies descrambling and decodingof FEC, if any, independently on each data stream after hierarchicalmodulation aware de-multiplexing of the demodulator output.

FIG. 7 illustrates a hierarchical modulation enabled MIMO transmitter700 according to an embodiment of the invention. Here the MIMOtransmitter 700 is capable of transmitting two data streams, each ofwhich is subject to hierarchical modulation, e.g., first data streamcomprises base stream A and enhanced stream B, and second data streamcomprises base stream C and enhanced stream C. In this exemplaryembodiment of the invention, the MIMO transmitter 700 facilitates OFDMin, for example, an LTE downlink.

MIMO transmitter 700 comprises encoders 710A, 712A, 710B, and 712B, andscramblers 720A, 722A, 720B, and 722B. Encoder 710A and scrambler 720Aoperate on base stream A. Encoder 712A and scrambler 722A operate onenhanced layer B. Encoder 710B and scrambler 720B operate on base streamC. Encoder 712B and scrambler 722B operate on enhanced layer D. Theencoded and scrambled base stream A and enhanced stream B aremultiplexed via hierarchical modulation aware multiplexer 730A. Theencoded and scrambled base stream C and enhanced stream D aremultiplexed via hierarchical modulation aware multiplexer 730B.

As mentioned above, the implementation of modulation mappers 740A and740B and resource mappers 750A and 750B are readily apparent to one ofordinary skill in the art. The implementation of the layer mapper 744 isalso apparent to one of ordinary skill in the art. In an aspect of theinvention, the layer mapper 744 may process multiple streams to generateoutput MIMO layers. Implementation of the precoder 748 is apparent toone of ordinary skill in the art. In an aspect of the invention, theprecoder 748 may further process layers to improve communicationefficiency.

FIG. 8 illustrates a hierarchical modulation enabled MIMO transmitter800 according to an embodiment of the invention. Here, the transmitter800 facilitates single carrier frequency-division multiple access(SC-FDMA) multiplexing in, for example, an LTE uplink. MIMO transmitter800 comprises the circuitry components of transmitter 700 in addition todiscrete Fourier transform (DFT) modules 846A and 846B, theimplementation of which is apparent to one of ordinary skill in the art.

FIG. 9 illustrates a hierarchical modulation enabled MIMO receiver 900according to an embodiment of the invention. In this exemplaryembodiment of the invention, the MIMO receiver 900 facilitatesorthogonal frequency-division multiplexing (OFDM) in, for example, anLTE downlink. MIMO receiver 900 comprises a fast Fourier transform (FFT)algorithms 910A and 910B, a resource demappers 920A and 920B, afrequency domain equalizer 930, and codeword mapper 938, theimplementation of which is apparent to one of ordinary skill in the art.In an aspect of the invention, codeword mapper 938 may receive MIMOlayer inputs and convert them to separate MIMO codeword streams.

First and second MIMO codeword streams are processed by demodulators940A and 940B, and hierarchical modulation aware demultiplexers 950A and950B. Demultiplexers 950A and 1350B split the first data stream intobase stream A and enhanced stream B, and split the second data streaminto base stream C and enhanced stream D, respectively. Base stream A isdescrambled and decoded by descrambler 960A and decoder 970A,respectively. Enhanced stream B is descrambled and decoded bydescrambler 962A and decoder 972A, respectively. Base stream C isdescrambled and decoded by descrambler 960B and decoder 970B,respectively. Enhanced stream D is descrambled and decoded bydescrambler 962B and decoder 972B, respectively.

FIG. 10 illustrates a hierarchical modulation enabled MIMO receiver 1000according to an embodiment of the invention. Here, the receiver 1000facilitates single carrier frequency-division multiple access (SC-FDMA)multiplexing in, for example, an LTE uplink. MIMO receiver 1000comprises the circuitry components of receiver 900 in addition toinverse discrete Fourier transform IDFT modules 1034A and 1034B, theimplementation of which are apparent to one of ordinary skill in theart.

Hybrid automatic repeat request (hybrid ARQ or HARQ) is a combination ofhigh-rate FEC and ARQ error-control. In standard ARQ, redundant bits areadded to data to be transmitted using an error-detecting (ED) code suchas a cyclic redundancy check (CRC). HARQ is the retransmission ofpreviously transmitted data or additional FEC bits to allow FEC torecover data that was unrecoverable solely from the originaltransmission.

Although certain systems tend to resend at the modulation and codingscheme (MCS) of the original transmission, technically speaking, HARQretransmissions may use any MCS. This is an important consideration forefficient interaction between hierarchical modulation and HARQ.Retransmitting at the original MCS would require both streams A and B tobe retransmitted, which would be inefficient if one of the streams hadbeen received correctly.

In such a case where a system requires an identical retransmission, thetwo streams may be treated as a single HARQ process or as separate HARQprocesses. A device which successfully received its originaltransmission may ignore the data received in the retransmission. Thedevice must be made aware from scheduling signaling that it is receivinga retransmission rather than an original transmission of new data.

However, since determination of successful receipt of the data for astream, for example via FEC decode, is conducted after de-multiplexingin the receive chain, each stream can be treated as an independent HARQprocess (i.e., retransmission timing and parameters may be independentfor the two streams). If, for a hierarchical modulation transmission,the data for stream A is received correctly, but the data for stream Bis not received correctly, only the data from stream B need beretransmitted (or additional parity transmitted, depending on the formof HARQ used). Because this data is independent, it can be retransmittedas a single user transmission using any appropriate MCS or may betransmitted as part of a new hierarchical modulation transmission.

Hierarchical modulation can also be applied in the uplink (UL) for twodata streams from the same UE. If all applications (e.g., email, VoIP,streaming video, adaptive streaming video, FTP, etc.) and transportprotocols (e.g., TCP, UDP) were equal, a UE would be commanded totransmit at the most efficient modulation that still achieves anacceptable bit error rate when the signal is received at the basestation. However, a UE may have multiple UL services active at any pointin time. These services may have different tolerances to bit errors ordelays. For instance video streamed over TCP may desire a lower biterror rate (BER) than video streamed over UDP. The lower bit error ratemay be desirable in this instance to minimize freeze-causing TCPretransmissions. In another example, voice over IP may be intolerant ofthe delays associated with TCP retransmissions and may desire a lowerbit error rate than a background email update or a file download whichcan tolerate such delays.

The desired modulation rate for a UE uplink may be chosen to achieve atarget BER or block error rate (BLER) given the current physical layersignal quality metrics (e.g., SNR, RSSI, etc.). The target BER may be afunction of the UE's services and their characteristics includingapplication and transport protocol. Preferably, each service would havea target BER. One skilled in the art would understand that a target BER,based on applications and transport protocols, could also be chosen foran entire group of UL services, such as the services reported jointly inan LTE buffer status report, including the group of all UL servicesactive at a UE.

If the difference in bit error rate tolerance is such that the preferredmodulation for each of a pair of streams, or groups of streams, isdifferent, hierarchical modulation in the uplink transmission of the UEmay be used to increase the overall throughput of the uplink relative tohaving the UE transmit both streams at the more robust modulation ortransmitting them serially with different modulations.

FIG. 11 illustrates a transmitter 1100, such as might be used in a UE,according to an embodiment of the invention. Here, the transmitter 1100is processing an SC-FDM uplink on which hierarchical modulation can beapplied. For example, the transmitter 1100 may multiplex two streams(i.e., stream A and stream B) onto a higher order modulation, such asQAM-16, with stream A requiring a more robust modulation being mapped tothe bits defining the quadrant, effectively QPSK modulation, and themore error or delay tolerant stream B being mapped to the two bits thatgovern the position of a QAM-16 constellation point within the quadrant(e.g., see FIG. 2A). The transmitter 1100 comprises encoders 1110A and1110B, scramblers 1120A and 1120B, a hierarchical modulation awaremultiplexer 1130, a modulation mapper 1140, a DFT module 1145, aresource mapper 1150, and an inverse fast Fourier transform algorithm(IFFT) 1160. Scrambling and encoding may be optional.

FIG. 12 illustrates a complimentary hierarchical modulation awarereceiver 1200, such as might be used in a base station, for the SC-FDMuplink, according to an embodiment of the invention. The receiver 1200comprises a fast Fourier transform (FFT) algorithm 1210, a resourcedemapper 1220, a frequency domain equalizer 1230, an IDFT module 1235, ademodulator 1240, and a hierarchical modulation aware demultiplexer1250. The base station would receive the stream, for instance, as QAM-16and then de-multiplex the bits (via demultiplexer 1250) indicating thequadrant into stream A and the remaining bits into stream B (e.g., seeFIG. 2A). The reception path in the UE implements the reverse of theencoding and scrambling techniques implemented in the transmit path inthe UE via descramblers 1260A and 1260B, and decoders 1270A and 1270B.

Similarly, one of ordinary skill in the art readily understands how toapply the above-described techniques and embodiments to an OFDM or OFDMAuplink.

FIG. 13 illustrates a process 1300 for uplink hierarchical modulation oftwo data streams transmitted from the same UE according to an embodimentof the invention. The process 1300 begins by the base station and the UEnegotiating (step 1301) in order to make sure that both devices arecapable of supporting hierarchical modulation and currently areoperating under conditions that allow them to engage in the hierarchicalmodulation scheme. For example, the base station or the UE may notcurrently have a sufficient channel condition to allow for engagement inthe hierarchical modulation scheme. In that case, hierarchicalmodulation is impractical. Negotiation is an optional step because insome embodiments the wireless system may require the base station andthe UE to periodically report its ability to engage in the hierarchicalmodulation scheme. Similarly, in an embodiment of the invention, thewireless system may require that all devices in the system supporthierarchical modulation and negotiation would be unnecessary. This stepmay be initiated by the UE or the base station as the followingdescribes in greater detail.

The current data streams supporting services in a particular UE areidentified (step 1302) as candidates for pairing in the uplinkhierarchical modulation scheme. Each data stream may be classified as acandidate for the base layer or the enhanced layer of the hierarchicalmodulation scheme, or may be classified as a candidate for both layers.The determination of which candidate layer each data stream may beidentified with may depend on the policy, the class of service,tolerance to impairments such as bit errors or retransmissions, andother considerations and requirements associated with that data stream.The functionality of this step may be performed in the UE, the basestation or in another node in the network. If the data stream candidateselection is performed in a network node other than the base station orthe UE, then the list of data stream candidates for the base layer andthe enhanced layer will need to be sent to the entity (either the basestation or the UE) that performs pairing of the candidate data streamsinto hierarchical modulation pairs.

The candidate data streams are reviewed and certain candidates areselected and paired (step 1303) into hierarchical modulation pairs. Asstated above, this step may be performed by the UE or the base station.The hierarchical modulation pair is comprised of a data stream from thebase layer candidate list and a data stream from the enhanced layercandidate list. In an embodiment in which the UE performs this step, theUE may conduct this hierarchical modulation pairing after conducting thecandidate identification step. In an embodiment in which the basestation performs this step, the base station may wait to perform thishierarchical modulation pairing until receiving a bandwidth request fromthe UE associated with the user streams. Regardless of which entityperforms this step, the matching of candidate data streams may beconducted by first identifying data stream candidates from each of thebase layer and enhanced layer candidate lists that have data pending foruplink transmission. Next, a candidate data stream from the base layerlist and a candidate data stream from the enhanced layer list areselected to create a hierarchical modulation pair.

The UE requests (step 1304) uplink bandwidth from the base station tosupport uplink transmission of the data associated with the data streamsof the hierarchical modulation pair. As mentioned above, if the UE isperforming the pairing step then this bandwidth request is sent afterthe pairing step. However, if the base station is performing the pairingstep then the base station may wait until after it receives a bandwidthrequest from the UE before performing the pairing step. In theembodiment in which the UE is performing the pairing step, the userequipment includes an indication that hierarchical modulation will beused in the bandwidth request that is sent to the base station.

The base station grants the bandwidth request by sending (step 1305) abandwidth allocation in the downlink channel to the UE. Upon receivingthe bandwidth allocation, the UE proceeds to multiplex (step 1306) thedata to be sent in the uplink for the two data streams associated withthe hierarchical modulation pair. The multiplexing of the data for thetwo data streams is performed after the forward error correction and thescrambling, but before modulation. In other embodiments of theinvention, forward error correction and/or the scrambling may not beutilized, but to the extent that those functions are present they areperformed prior to the multiplexing. The resulting single multiplexeddata stream is comprised of data from the base layer data stream anddata from the enhanced layer data stream. Next, the single multiplexeddata stream is transmitted (step 1307) from the UE over the allocateduplink bandwidth to the base station.

The base station receives (step 1308) the single multiplexed data streamand de-multiplexes the data after demodulation of the received signal.In this manner, the base station retrieves base layer data, i.e.,protocol data units (PDUs), and enhanced layer data, i.e., PDUs, fromthe received single multiplexed data stream. The base station then maps(step 1309) the retrieved PDUs to the appropriate data streamsassociated with the hierarchical modulation pair. This mapping of theretrieved PDUs to the correct data streams may be performed byinspecting the header information in each PDU or by relying uponhierarchical data stream pair mapping information contained in thebandwidth request received from the user equipment.

The foregoing description of the functional steps presented in FIG. 13is an exemplary embodiment of the invention and one of ordinary skill inthe art appreciates that these functional steps can be performed in adifferent order and by different entities while still achieving theuplink hierarchical modulation scheme for two data streams of the sameUE.

FIG. 14 illustrates a UE initiated hierarchical modulation process 1400in an uplink for two data streams from the same UE according to anembodiment of the invention. Here, the UE not only initiates thehierarchical modulation scheme, but also performs the candidate datastream identification and candidate pairing steps before sending anuplink bandwidth request to the base station along with an indicationthat hierarchical modulation will be used in the uplink. Particularly,the process 1400 begins with the UE initiating (step 1401) hierarchicalcapability negotiation in order to determine whether both devices arecapable of supporting hierarchical modulation and currently areoperating under conditions that allow them to engage in the hierarchicalmodulation scheme. The base station provides (step 1402) the UE with anindication of its current support for hierarchical modulation. The UEidentifies (step 1403) candidate data streams for pairing based on, forexample, policy, class of service, tolerance to impairments such as biterrors or retransmissions, and other considerations and requirementsassociated with that data stream. The UE pairs (step 1405) at least twocandidate data streams having pending data. The UE then sends (step1407) an uplink bandwidth request to the base station indicating thathierarchical modulation will be used.

The base station receives (step 1408) the uplink bandwidth request fromthe UE. The base station then sends (step 1410) a response indicatinggranted uplink bandwidth allocating to the UE in downlink, which isreceived (step 1411) by the UE. Upon receiving the bandwidth allocation,the UE proceeds to multiplex (step 1413) the data to be sent in theuplink for the two data streams associated with the hierarchicalmodulation pair. The multiplexing of the data for the two data streamsis preferably performed after the forward error correction and thescrambling, but before modulation. The single multiplexed data stream isthen transmitted (step 1415) by the UE over the allocated uplinkbandwidth to the base station. The base station receives (step 1416) thesingle multiplexed data stream and de-multiplexes the PDUs afterdemodulation. The base station maps (step 1418) the retrieved PDUs tothe data streams associated with the hierarchical modulation pair byeither inspecting the header information in each PDU or by relying uponhierarchical data stream pair mapping information contained in thebandwidth request received from the UE.

FIG. 15 illustrates a base station initiated hierarchical modulationprocess 1500 in an uplink for two data streams transmitted from the basestation according to an embodiment of the invention. Here, the basestation not only initiates the hierarchical modulation scheme, but alsoperforms the candidate data stream identification and candidate pairingsteps after receiving an uplink bandwidth request from the UE. Theuplink bandwidth request includes information regarding which UE datastreams have data pending at the UE for sending in the uplink. In thisembodiment of the invention, the base station may also send controlinformation regarding the hierarchical modulation pair to the UE via acontrol channel so that the UE has notice that hierarchical modulationshould be used for the identified data streams associated with thehierarchical modulation pair in the uplink.

The process 1500 begins with the base station initiating (step 1501)hierarchical capability negotiation in order to determine whether bothdevices are capable of supporting hierarchical modulation and currentlyare operating under conditions that allow them to engage in thehierarchical modulation scheme. The UE provides (step 1502) the basestation with an indication of its current support for hierarchicalmodulation. The base station identifies (step 1503) candidate datastreams for pairing based on, for example, policy, class of service,tolerance to impairments such as bit errors or retransmissions, andother considerations and requirements associated with that data stream.The UE sends (step 1504) one or more uplink bandwidth requests to thebase station. Upon receiving (step 1505) the uplink bandwidth requests,the base station pairs (step 1507) at least two candidate data streamshaving pending data. The base station then sends (step 1509) a responseindicating a granted uplink bandwidth allocation and hierarchicalmodulation control information to the UE in the downlink, which isreceived (step 1510) by the UE. Upon receiving the bandwidth allocation,the UE proceeds to multiplex (step 1512) the data to be sent in theuplink for the two data streams associated with the hierarchicalmodulation pair. The multiplexing of the data for the two data streamsis preferably performed after the forward error correction and thescrambling, but before modulation. The single multiplexed data stream isthen transmitted (step 1514) by the UE over the allocated uplinkbandwidth to the base station. The base station receives (step 1515) thesingle multiplexed data stream and de-multiplexes the PDUs afterdemodulation. The base station maps (step 1517) the retrieved PDUs tothe data streams associated with the hierarchical modulation pair byeither inspecting the header information in each PDU or by relying uponhierarchical data stream pair mapping information contained in thebandwidth request received from the UE

As mentioned, one or more steps of the aforementioned processes may beperformed by other network nodes.

One of the main challenges with hierarchical modulation is theintroduction of inter-layer interference (ILI) due to the reduction ofthe noise margin of the base layer by the introduction of the enhancedlayer(s). The noise margin in transmitting the base layer only isrepresented by the distance between the gray dots in FIG. 2B. Theaddition of the enhanced layer reduces the noise margin to the distancebetween the higher order constellation points in the figure, whichresults in a higher bit error rate (BER) for the base layer receiversand affects the overall throughput of the system.

FIG. 16 illustrates constellation diagrams of an implementation ofhierarchical modulation. The base layer employs QPSK modulation (shownon the top left), which maps to 2 bits per symbol. The enhanced layeralso carries 2 bits per symbol requiring a QAM16 modulated signal tocarry both layers. Here, the first and third bits of each symbol areused to indicate the quadrant. The minimum Euclidean distance (MED) ord_(min) is a function of α and β in the figure. In case of the baselayer alone, the MED would have been:d _(min)=2αHowever, with the superimposing of the enhanced layer, the MED isreduced to be:d _(min)=min(2(α−β),2α,2β)The reduction in MED results in more ambiguity in the demodulator whichis attempting to demodulate the base layer by, for example, discerningthe quadrant. This then results in more demodulation errors. This isespecially true when the higher order modulation constellation necessaryto carry both the base and enhanced layers has constellation pointsclose to one of the quadrature or inphase axis.

Enhancing the hierarchical modulation reduces the effect of ILI. One wayto reduce ILI is via rotation of the constellation points carrying theenhanced layer information. FIG. 17 illustrates a QAM 16 hierarchicalmodulation constellation with rotated constellation points allowingbetter discernment of the base layer using QPSK demodulation while usinga modified QAM16 demodulation to discern the constellation pointsconveying the enhanced layer data. FIG. 18 illustrates a QAM 64constellation with rotated constellation points which allow better pointdiscernment when receiving a base layer using either QPSK or QAM 16while using a modified QAM 64 demodulation to discern the constellationpoints conveying the enhanced layer data. Rotation increases the noisemargin for the base layer stream with little increase to systemcomplexity. Selection of the rotation angle is done via optimizingdifferent criteria in the system performance. For example, theachievable spectral efficiency may be maximized by optimizing Euclideandistance between two higher order constellation points that resolve todifferent lower order constellation points in the modulation scheme usedto receive the base layer.

Another approach for mitigating ILI is done via muting of constellationpoints, as illustrated in FIG. 19. Here, muting increases the noisemargin as it increases the Euclidean distance between higher orderconstellation points that resolve to different lower order constellationpoints in the modulation scheme used to receive the base layer. In thisexample, a QPSK base layer and the logical equivalent of a QAM8 (3 bitsper symbol data carrying capacity) enhanced layer are transmitted usinga QAM64 constellation with 32 out of the 64 points muted, which ispossible because the QAM64 constellation has 6 bits per symbol carryingcapacity. Muting half the points leaves the remaining 32 symbols with 5bits per symbol carrying capacity. This technique is sufficient forcarrying the 2 bits per symbol of the QPSK base layer and the 3 bits persymbol of the logical QAM8 enhanced layer. Both the QPSK base layer andthe logical QAM8 enhanced layer are encoded using Grey coding, theimplementation of which is apparent to one of ordinary skill in the art.The respective binary bits of the two streams are separated by a “|”character for ease in visually identifying the bits belonging to eachstream. One of ordinary skill in the art readily appreciates thatdifferent combinations or different numbers of constellation points maybe muted and coding other than Grey coding may be used. For example, ifonly the 28 constellation points directly adjacent to the I and Q axiswere muted, the enhanced layer would have 9 constellation points (i.e.,9 additional positions in each quadrant) rather than 8, giving acarrying capacity of log₂(9) (approximately 3.17) bits per symbol forthe enhanced layer.

FIG. 20 is a communication network in which features disclosed hereincan be implemented in accordance with aspects of the invention. A macroaccess node 2010 is connected to a core network 2002 through a backhaulconnection 2070. In an embodiment, the backhaul connection 2070 is abidirectional link or two unidirectional links. The direction from thecore network 2002 to the macro access node 2010 is referred to as thedownstream or downlink direction. The direction from the macro accessnode 2010 to the core network 2002 is referred to as the upstream oruplink direction. Subscriber stations 2050(1) and 2050(4) can connect tothe core network 2002 through the macro access node 2010. Wireless links2090 between subscriber stations 2050(1) and 2050(4) and the macroaccess node 2010 are bidirectional point-to-multipoint links, in anembodiment. The direction of the wireless links 2090 from the macroaccess node 2010 to the subscriber stations 2050(1) and 2050(4) isreferred to as the downlink or downstream direction. The direction ofthe wireless links 2090 from the subscriber stations 2050(1) and 2050(4)to the macro access node 2010 is referred to as the uplink or upstreamdirection. Subscriber stations are sometimes referred to as userequipment, users, user devices, handsets, terminal nodes, or userterminals and are often mobile devices such as smart phones or tablets.The subscriber stations 2050(1) and 2050(4) access content over thewireless links 2090 using access node, such as the macro access node2010.

In the network configuration illustrated in FIG. 20, an office building2020(1) causes a coverage shadow 2004. A pico access node 2030 canprovide coverage to subscriber stations 2050(2) and 2050(5) in thecoverage shadow 2004. The pico access node 2030 is connected to the corenetwork 2002 via a backhaul connection 2070. The subscriber stations2050(2) and 2050(5) may be connected to the pico access node 2030 vialinks that are similar to or the same as the wireless links 2090 betweensubscriber stations 2050(1) and 2050(4) and the macro access node 2010.

In office building 2020(2), an enterprise femtocell access node 2040provides in-building coverage to subscriber stations 2050(3) and2050(6). The enterprise femtocell access node 2040 can connect to thecore network 2002 via an internet service provider network 2001 byutilizing a broadband connection 2060 provided by an enterprise gateway2003.

In addition, internet service provider network 2001 may also provide abroadband connection between core network 2002 and cable head end 2080,which may be a cable head end of a local, regional or national digitalcable service. Cable head end 2080 is connected to a large number of settop boxes and cable modems, such as cable modem 2081, by a network ofcables or other wired connections. Cable modem 2081 may be provided in aresidence or a business location and provides internet connectivity tosubscriber stations 2050(7) and 2050(8). In this regard, cable modem2081 is connected to access node 2085 which provides wireless coverageto subscriber station 2050(7) and may be, for instance, an LTEresidential femtocell access node or a WiFi access node. Subscriberstation 2050(8) may be directly wired to cable modem 2081 via anEthernet connection or other wired connection.

FIG. 21 is a functional block diagram of an access node 2175 inaccordance with aspects of the invention. In various embodiments, theaccess node 2175 may be a mobile WiMAX base station (BS), a globalsystem for mobile (GSM) wireless base transceiver station (BTS), aUniversal Mobile Telecommunications System (UMTS) NodeB, an LTE evolvedNode B (eNB or eNodeB), a cable modem head end, or other wireline orwireless access node of various form factors. For example, the macroaccess node 2010, the pico access node 2030, the enterprise femtocellaccess node 2040, or access node 2085 of FIG. 20 may be provided, forexample, by the access node 2175 of FIG. 21. The access node 2175includes a processor module 2181. The processor module 2181 is coupledto a transmitter-receiver (transceiver) module 2179, a backhaulinterface module 2185, and a storage module 2183.

The transmitter-receiver module 2179 is configured to transmit andreceive communications with other devices. In many implementations, thecommunications are transmitted and received wirelessly. In suchimplementations, the access node 2175 generally includes one or moreantennae for transmission and reception of radio signals. In otherimplementations, the communications are transmitted and received overphysical connections such as wires or optical cables. The communicationsof the transmitter-receiver module 2179 may be with terminal nodes.

The backhaul interface module 2185 provides communication between theaccess node 2175 and a core network. The communication may be over abackhaul connection, for example, the backhaul connection 2070.Communications received via the transmitter-receiver module 2179 may betransmitted, after processing, on the backhaul connection. Similarly,communication received from the backhaul connection may be transmittedby the transmitter-receiver module 2179. Although the access node 2175of FIG. 21 is shown with a single backhaul interface module 2185, otherembodiments of the access node 2175 may include multiple backhaulinterface modules. Similarly, the access node 2175 may include multipletransmitter-receiver modules. The multiple backhaul interface modulesand transmitter-receiver modules may operate according to differentprotocols.

The processor module 2181 can process communications being received andtransmitted by the access node 2175. The storage module 2183 stores datafor use by the processor module 2181. The storage module 2183 may alsobe used to store computer readable instructions for execution by theprocessor module 2181. The computer readable instructions can be used bythe access node 2175 for accomplishing the various functions of theaccess node 2175. In an embodiment, the storage module 2183 or parts ofthe storage module 2183 may be considered a non-transitory machinereadable medium. For concise explanation, the access node 2175 oraspects of it are described as having certain functionality. It will beappreciated that in some aspects, this functionality is accomplished bythe processor module 2181 in conjunction with the storage module 2183,transmitter-receiver module 2179, and backhaul interface module 2185.Furthermore, in addition to executing instructions, the processor module2181 may include specific purpose hardware to accomplish some functions.

FIG. 22 is a functional block diagram of a terminal node in accordancewith aspects of the invention. In this regard, the term “terminal node”may refer to a subscriber station (as in FIG. 20), a user equipment, amobile phone, a cellular phone, a user device or other network nodeoperated by a user. The terminal node 2200 can be used for viewingstreaming video. In various example embodiments, the terminal node 2200may be a mobile device, for example, a smartphone or tablet or notebookcomputer. The terminal node 2200 includes a processor module 2220. Theprocessor module 2220 is communicatively coupled to transmitter-receivermodule (transceiver) 2210, user interface module 2240, and storagemodule 2230. The processor module 2220 may be a single processor,multiple processors, or a combination of one or more processors andadditional logic such as application-specific integrated circuits (ASIC)or field programmable gate arrays (FPGA).

The transmitter-receiver module 2210 is configured to transmit andreceive communications with other devices. For example, thetransmitter-receiver module 2210 may communicate with a cellular orbroadband base station such as an LTE evolved node B (eNodeB) or WiFiaccess point (AP). In example embodiments where the communications arewireless, the terminal node 2200 generally includes one or more antennaefor transmission and reception of radio signals. In other exampleembodiments, the communications may be transmitted and received overphysical connections such as wires or optical cables and thetransmitter/receiver module 2210 may be an Ethernet adapter or cablemodem. Although the terminal node 2200 is shown with a singletransmitter-receiver module 2210, other example embodiments of theterminal node 2200 may include multiple transmitter-receiver modules.The multiple transmitter-receiver modules may operate according todifferent protocols.

The terminal node 2200, in some example embodiments, provides data toand receives data from a person (user). Accordingly, the terminal node2200 includes a user interface module 2240. The user interface module2240 includes modules for communicating with a person. The userinterface module 2240, in an exemplary embodiment, may include a displaymodule 2245 for providing visual information to the user, includingdisplaying video content. In some example embodiments, the displaymodule 2245 may include a touch screen which may be used in place of orin combination with a keypad connected to the user interface module2240. The touch screen may allow graphical selection of inputs inaddition to alphanumeric inputs.

In an alternative example embodiment, the user interface module 2240 mayinclude a computer interface, for example, a universal serial bus (USB)interface, to interface the terminal node 2200 to a computer. Forexample, a wireless modem, such as a dongle, may be connected, by awired connection or a wireless connection, to a notebook computer viathe user interface module 2240. Such a combination may be considered tobe a terminal node 2200. The user interface module 2240 may have otherconfigurations and include hardware and functionality such as speakers,microphones, vibrators, and lights.

The processor module 2220 can process communications received andtransmitted by the terminal node 2200. The processor module 2220 canalso process inputs from and outputs to the user interface module 2240.The storage module 2230 may store data for use by the processor module2220, including images or metrics derived from images. The storagemodule 2230 may also be used to store computer readable instructions forexecution by the processor module 2220. The computer readableinstructions can be used by the terminal node 2200 for accomplishing thevarious functions of the terminal node 2200. Storage module 2230 canalso store received content, such as video content that is received viatransmitter/receiver module 2210.

The storage module 2230 may also be used to store photos and videos. Inan example embodiment, the storage module 2230 or parts of the storagemodule 2230 may be considered a non-transitory machine readable medium.In an example embodiment, storage module 2230 may include a subscriberidentity module (SIM) or machine identity module (MIM).

For concise explanation, the terminal node 2200 or example embodimentsof it are described as having certain functionality. It will beappreciated that in some example embodiments, this functionality isaccomplished by the processor module 2220 in conjunction with thestorage module 2230, the transmitter-receiver module 2210 and the userinterface module 2240. Furthermore, in addition to executinginstructions, the processor module 2220 may include specific purposehardware to accomplish some functions.

The foregoing described aspects and features are susceptible to manyvariations. Additionally, for clarity and concision, many descriptionsof the aspects and features have been simplified. For example, thefigures generally illustrate one of each type of device (e.g., oneaccess node, one terminal node), but a communication system may havemany of each type of device. Similarly, many descriptions useterminology and structures of a specific wireless standard such as LTE,WiMAX, GSM, and the like. However, the disclosed aspects and featuresare more broadly applicable, including for example, other types ofcommunication systems.

Those of skill will appreciate that the various illustrative logicalblocks, modules, units, and algorithm steps described in connection withthe embodiments disclosed herein can often be implemented as electronichardware, computer software, or combinations of both. To clearlyillustrate this interchangeability of hardware and software, variousillustrative components, blocks, modules, and steps have been describedabove generally in terms of their functionality. Whether suchfunctionality is implemented as hardware or software depends upon theparticular constraints imposed on the overall system. Skilled personscan implement the described functionality in varying ways for eachparticular system, but such implementation decisions should not beinterpreted as causing a departure from the scope of the invention. Inaddition, the grouping of functions within a unit, module, block, orstep is for ease of description. Specific functions or steps can bemoved from one unit, module, or block without departing from theinvention.

The various illustrative logical blocks, units, steps and modulesdescribed in connection with the embodiments disclosed herein, and thoseprovided in the accompanying documents, can be implemented or performedwith a processor, such as a general purpose processor, a digital signalprocessor (DSP), an application specific integrated circuit (ASIC), afield programmable gate array (FPGA) or other programmable logic device,discrete gate or transistor logic, discrete hardware components, or anycombination thereof designed to perform the functions described herein,and those provided in the accompanying documents. A general-purposeprocessor can be a microprocessor, but in the alternative, the processorcan be any processor, controller, microcontroller, or state machine. Aprocessor can also be implemented as a combination of computing devices,for example, a combination of a DSP and a microprocessor, a plurality ofmicroprocessors, one or more microprocessors in conjunction with a DSPcore, or any other such configuration.

The steps of a method or algorithm and the processes of a block ormodule described in connection with the embodiments disclosed herein,and those provided in the accompanying documents, can be embodieddirectly in hardware, in a software module executed by a processor, orin a combination of the two. A software module can reside in RAM memory,flash memory, ROM memory, EPROM memory, EEPROM memory, registers, harddisk, a removable disk, a CD-ROM, or any other form of storage medium.An exemplary storage medium can be coupled to the processor such thatthe processor can read information from, and write information to, thestorage medium. In the alternative, the storage medium can be integralto the processor. The processor and the storage medium can reside in anASIC. Additionally, device, blocks, or modules that are described ascoupled may be coupled via intermediary device, blocks, or modules.Similarly, a first device may be described a transmitting data to (orreceiving from) a second device when there are intermediary devices (forinstance, a relay) that couple the first and second device and also whenthe first device is unaware of the ultimate destination of the data.

The above description of the disclosed embodiments is provided to enableany person skilled in the art to make or use the invention. Variousmodifications to these embodiments will be readily apparent to thoseskilled in the art, and the generic principles described herein can beapplied to other embodiments without departing from the spirit or scopeof the invention. Thus, it is to be understood that the description anddrawings presented herein represent particular aspects and embodimentsof the invention and are therefore representative examples of thesubject matter that is broadly contemplated by the present invention. Itis further understood that the scope of the present invention fullyencompasses other embodiments that are, or may become, obvious to thoseskilled in the art and that the scope of the present invention isaccordingly not limited by the descriptions presented herein.

What we claim is:
 1. A method for performing hierarchical modulation by an access node within a communications network, the method comprising the steps of: identifying, by the access node, a plurality of user devices within the communications network for hierarchical modulation reception at least by: acquiring data about the user devices within the communications network, the data comprising channel quality information; and determining which user device of the identified user devices for hierarchical modulation reception is to receive a base layer and which user device of the identified user devices for hierarchical modulation reception is to receive an enhanced layer at least by: distributing the user devices into the base layer based on modulation schemes comprising a most robust modulation and an intermediate modulation and into the enhanced layer based on modulation schemes comprising the intermediate modulation and a least robust modulation; and sending, via a transceiver in the access node, control information to each of the identified user devices, the control information comprising an identification of a shared radio resource for use by two of the identified user devices in support of hierarchical modulation reception.
 2. The method of claim 1, further comprising the step of receiving a measurement report from a user device, wherein the measurement report comprises the channel quality information.
 3. The method of claim 1, further comprising the step of mapping a base layer stream and an enhanced layer stream into a hierarchical modulation transmission, wherein the base layer stream is designated for reception by the identified user device determined to receive the base layer and the enhanced layer stream is designated for reception by the identified user device determined to receive the enhanced layer.
 4. The method of claim 1, wherein the control information indicates an assigned layer in hierarchical modulation for the respective identified user device.
 5. The method of claim 1, the step of identifying further comprises: excluding the user devices having the data not allowing hierarchical modulation, wherein the data comprises service level agreements (SLAs) or quality of service (QoS) profiles.
 6. The method of claim 1, the step of distributing further comprises: for the user devices operating at the most robust modulation, checking the measurement report received from each of the user devices to determine whether a signal quality of a signal received by the user device allows hierarchical modulation; and determining the user device for hierarchical modulation reception is to receive the base layer if the signal quality allows hierarchical modulation.
 7. The method of claim 1, the step of distributing further comprises: for the user devices operating at the least robust modulation, checking whether each of the user devices is capable of supporting hierarchical modulation; and determining the user device for hierarchical modulation reception is to receive the enhanced layer if the user device is capable of supporting hierarchical modulation.
 8. The method of claim 1, the step of distributing further comprises: for the user devices operating at the intermediate modulation, checking whether each of the user devices is capable of supporting hierarchical modulation; checking the measurement report received from each of the user devices capable of supporting hierarchical modulation to determine whether a signal quality of a signal received by the user device allows hierarchical modulation; determining the user device is to receive both the base layer and the enhanced layer if the signal quality allows hierarchical modulation with the user device receiving the base layer; and determining the user device is to receive the enhanced layer if the signal quality does not allow hierarchical modulation with the user device receiving the base layer.
 9. A method for hierarchical modulation reception by a user equipment within a communications network, the method comprising the steps of: transmitting a channel quality information; receiving, via a transceiver in the user equipment in response to transmitting the channel quality information, control information from an access node indicating an assigned layer of hierarchical modulation designated for the user equipment; receiving, via the transceiver in the user equipment, a hierarchical modulated transmission comprising a base layer and an enhanced layer, wherein the base layer comprises a transmission under a most robust modulation and a transmission under an intermediate modulation, the enhanced layer comprises a transmission under the intermediate modulation and a transmission under a least robust modulation from the access node; and utilizing only the assigned layer of the received hierarchical modulated transmission.
 10. The method of claim 9, wherein the control information further comprises an identification of a shared radio resource for use in hierarchical modulation reception by the user equipment. 